Moonshine still circa 1930s. Image credit:OldPictureMinnesota Public Radio points out that when it comes to weighing the benefits of ethanol for motor fuel, the devil is in the details...or more properly 'in the process.' Who knew that ethanol fuel-production fermentation tanks had antibiotics such as penicillin added? No kidding. This widespread operating practice may have indirect human and animal health impacts. Read on to find out how, and why.

Antibiotic residues may threaten the economic viability of ethanol fuel industry.The operating margins of ethanol producers depend on the ability to sell the spent corn mash known as "distillers grain." When the price of ethanol dips, revenues from distillers grain are what keeps the producer in business. Hence, these days, the the sector's viability hinges on what animal food formulators are willing to pay.

Evidence is mounting that a fundamental process technology change may be necessary to keep the US EtOH industry functioning.

Several studies have linked the by-product known as distillers grain to elevated rates of E. coli in cattle. And now, distillers grain is facing further scrutiny because the Food and Drug Administration has found that it often contains antibiotics leftover from making ethanol.

FDA has decided to re-open the file on this issue, and what's coming out doesn't smell too good.

Among others, ethanol producers use penicillin and a popular antibiotic called virginiamycin to kill bacteria. And that raises two potential concerns. One is that these treatments might promote the growth of bacteria that are resistant to antibiotics. The development of these 'super-bugs' is a major concern in health care because they reduce the effectiveness of medicines. Mark von Keitz found some bacteria that were in fact resistant when he sampled bacteria at four Midwest ethanol plants several years ago.

The second concern is that the antibiotics could find their way to humans through the food chain. The U.S. Food and Drug Administration has taken a mostly a hands-off approach to the use of antibiotics in the ethanol industry. But amid increasing concerns over food safety in recent years the agency is taking a closer look.

Background and analysis.Beginning in the 1800's, wine makers added sodium meta-bisulfite, an oxygen scavenging, inorganic compound sold as the "camden tablet" or just "camden" to mashed fruit ready for fermentation. The primary purpose of adding it has always been to take out all the oxygen, starving out native yeasts and aerobic bacteria, and making way for cultivated yeast varieties that produce more alcohol, faster, once oxygen is again introduced.

A secondary benefit of adding the "sulfiting agent" is that small residues left in wine act as a preservative, preventing white wines from turning brown and any wine from losing aromatic qualities, thereby increasing shelf life. It's an antibiotic of sorts, and, secondarily, a preservative.

Note: Don't buy the wine industry line that sulfites are an absolute prerequisite for fermentation and that sulfites are naturally present in grapes. That's nonsense. Its relatively modern preservative and processing aid that keeps profits up.

Wine making practices predate the periodic table of elements by thousands of years. Does anyone seriously think that the wine served at the Last Supper had sodium meta-bisulfite added?

Confusion over this point is made worse by how sulfur is measured. Once in solution and exposed to luxurious amounts of oxygen, the sulfite is changed almost instantly to sulfate. Hence, you can not really measure sulfites in natural grape juice directly: not with easy accuracy, at any rate. What you can measure in a pre-fermentation mash, is such surrogate indicators as total sulfate or total sulfur; and results from those tests will reflect any lime sulfur that has been dusted on the vines as a pesticide, and which may either be taken up through the soil and into fruit, or simply remain on the fruit.

Important caveat: sulfur is registered as a "natural" substance suitable for organic grape production; so, this argument applies to all grapes used in fermentation.

Lets get back to the corn mash. Apparently, keeping out process-spoiling bacteria is the sought-after effect of antibiotics added to the fuel-ethanol fermentation equipment.

Why are antibiotics, and not sulfiting agents, added to fuel-ethanol fermenters?Possibly there were odor control problems with excess sulfate shifting to H2S in the distillers grain, such that cows refused it?

Maybe some of the sulfur partitioned into the small amount of water always found in ethanol, and stood a chance to gum up engines? Could be an issue whether distillation or membrane separation was used.

Will the biotic processes for cellulosic ethanol production also call for antibiotic use? What happens to the co-products of cellulosic ethanol production?

Who knows? More mysteries of green technology.

Risk management lesson that needs to be relearned.Green investors and process designers need absolutely to conduct life cycle risk management evaluations before rushing to market with scaled up process designs. I don't mean financial risk evaluation. I mean actual environmental assessment by third parties without pride of design and absent any financial interests in the business.